Professor Yashar Ganjali Department of Computer Science University of Toronto.

Transcription

1 Professor Yashar Ganjali Department of Computer Science University of Toronto

2 Announcements Final project proposal Guidelines have been posted on class website. Each project completed by groups of two students Use class mailing list to find teammates if you don t know anyone in class. 1 page proposal Due: Fri. Oct 16 th at 5PM Intermediate report Key technologies 2 pages Due: Fri. Nov. 13 th at 5PM 2

3 Announcements Cont d Final presentation In class during the last two weeks 15 minute presentation Final report Put everything together 5 pages Due: Fri. Nov. 27 th at 5pm Volunteer for lecture notes? 3

4 The Story Introduction to computer networks Internet vs. mail The science of networks Characteristics, graphs, scale-free networks, Last week: Computer networks and healthcare This week: Computer networks and business 4

5 Outline New business opportunities Online shopping Digital content Online trading Search engines and online advertisement How networks benefit small and large businesses Efficiency, communication Technologies that made it possible Ethernet Virtual private networks 5

6 Networks Create New Possibilities Online shopping Amazon, ebay, Targeted advertisement Online banking Online trading Currency exchange Stocks e-commerce Remote meetings 6

7 Online Shopping Internet can help with traditional shopping Retail E.g. order furniture online Much more convenient and flexible Peer-to-peer ebay, Kijiji, Craigslist, Check the order status, delivery, online Electronic payments Credit cards, PayPal, 7

8 Selling Digital Content Internet has also created new possibilities ebooks, mp3s, videos, TV, Amazon, Apple itunes, Netflix, These are new forms of traditional books, CDs, Advantages Faster delivery (almost instant) Convenience Access your library from anywhere Costs less Targeted advertisements and marketing Good for advertisers and customers (?) 8

9 Advertisement on the Internet New form of advertising Advertise while people are surfing the web Have access to more information Based on past browsing history you can find out about the user s interests and target them with more accurate ads Might be useful for the customer as well And less annoying Can cost less Compared to TV, billboards, 9

10 Online Trading Stocks, stock options, currency exchange all possible in today s Internet The most important issues here are Network reliability: order should not be lost Delay: extremely tight guarantees for timing required It s all about timing, timing, timing Ordinary users: seconds to minutes Trading companies: nano seconds to micro seconds Online Trader ISP One ISP Two 10

11 Delay in Computer Networks Delay has three major components: Transmission delay: how long it takes for your machine to inject the traffic into network Propagation delay: how long it takes for data to traverse the distance between source and destination Queueing delay: how long your data packets sit in queues (buffers) on Internet routers 11

13 Search Engines You can find new things by looking for keywords Not ideal but works Question.What is the ideal way? You can find new things to buy That s why advertising on the Internet is such a big success We spend a lot of time behind computers these days Question.how do search engines know how to sort web pages? 13

14 Detour: Search Engines Question. How do search engines find web pages related to your search? They have a large number of robots that constantly crawl the web. You can simply make your own crawler. Write a script that downloads a given web page. Extracts all the links. If a link has not been downloaded before Download and repeat. B D A F C E 14

15 How To Find the Best Match There might be many pages that have the given keyword. Question. How to sort these pages and find the best match? Technique # 1. Show any page that has the given keyword, sort based on how many times the keyword appears Or use font size, font shape (bold or italic, ) as guides on how important that keyword is Question. Does this work? Why? 15

16 Finding the Best Match Cont d Technique # 2: Use the number of links to this page as a clue. The more the number of links, the higher the rank of this page. Question. Does this work? Why? Both techniques are vulnerable to attacks Someone can easily increase the rank of their page by Increasing the font size, frequency of the keywords, Or by creating fake pages pointing to this page 16

17 Use Reputation as the Criteria Basic idea: assign a credibility score to each page. Repeatedly update credibility score of each page Divide the credibility score by the number of outgoing links, and distribute it among them

18 Use Reputation as the Criteria Basic idea: assign a credibility score to each page. Repeatedly update credibility score of each page Divide the credibility score by the number of outgoing links, and distribute it among them

19 Use Reputation as the Criteria Basic idea: assign a credibility score to each page. Repeatedly update credibility score of each page Divide the credibility score by the number of outgoing links, and distribute it among them Question.Where do we start? This is the basic idea behind PageRank which is used by Google

20 Why This Matters Good search results means people will use your search engine That s why Google doesn t charge us Also, you need to find good matches between search results and advertisements Can enhance your return Question.Is it just a matter of good matching? Text vs. picture vs. animation Size of the ad Where it appears on a page 20

22 Benefits of Using Networks in Business Networks allow sharing the cost of peripherals Printers Scanners Shared data storage... Improved communication Locally Remotely Work from home Or while traveling 22

23 Efficiency Data is readily available Rather than looking for a physical file Can serve customers faster And better: shared data Reduce errors and improve consistency All staff work from the same source of information Make standard manuals and guidelines available Data can be backed up and checked for consistency 23

25 What Technologies Made This Possible Ethernet is the dominant networking technology for Local Area Networks (LANs) Extremely simple to setup Most of the time, just plug your computer and it works Very inexpensive to setup and maintain Supports both wired and wireless networking Relatively high rates: 10Mb/s to 100Gb/s 25

26 How Does Ethernet Work First, we need an address Remember the mail example: This is how other computers know how to find you Two ways to assign an address to your computer Manual setup We call this static IP address assignment Automatic setup We call this one dynamic IP address assignment The protocol used is called DHCP (Dynamic Host Configuration Protocol) 26

27 How Do Nodes Talk in Ethernet Shared communication medium (wired or wireless) Can lead to collision Think of two or more people talking in the classroom We need some sort of coordination to avoid collision Only one person speaks at a time How do we do this in real life? 27

28 How Do Nodes Talk in Ethernet Cont d Here is how Ethernet solves this problem Listen: if nobody else is talking you can start Otherwise wait till they finish While talking keep listening Nobody else talks à done! Why? Somebody starts talking à collision In case of collision Choose a random time in the future Repeat Question: How long should we wait before retrying? 28

29 Wireless Networking in an Office Easier to setup No need to physically connect nodes Inexpensive Very flexible Can handle many computers Different types of devices Mobility: computers can be moved easily No need to reconfigure 29

30 And The Problems Lower rate compared to wired networks Mb/s compared to 100Mb/s 1Gb/s or higher Shared medium Limited number of wireless channels available All machines are on the same medium In wired, you can have point-to-point connection Less secure Your signal can be heard by people nearby 30

31 Virtual Private Networks (VPNs) Your employees might want to connect to their business network from home, or while traveling Many security concerns Virtual Private Networks make this possible Remotely connect to your work network As if you are sitting in your office Access to all resources (databases, peripherals, ) All communications are encrypted Question.How do you build a VPN? 31

32 Remote Collaboration A lot of people work from home these days Long distance collaborations Researchers, students/mentors, Tons of tools to make this possible Voice/video conferencing and presentations Online sharing of documents Collaborative writing Google docs, MS OneNote, Energy savings, impact on environment Makes sense financially as well; gas prices going up 32

33 Other Areas of Impact Outsourcing Computer networks bring resources closer Ideally, customer won t see a difference Business-to-business services Not only you can provide service to your customers You can buy and sell products and services to other businesses E-Commerce Information diffusion? Information is money Technologies for fast distribution and aggregation of news 33

34 Summary and Discussion Computer networks have already changed the way we do business Online shopping, digital content, trading, e-commerce, advertisements, They provide many benefits for small and large businesses Communication, resource sharing, What other areas can you think of? What are the technologies we need to work on today? 34